Barbara Morse was an S.H.I.E.L.D. agent whose assignments made her an ally of the jungle lord Ka-Zar. She subsequently used the costumed identity of the Huntress and later Mockingbird to expose the corrupt activities of certain S.H.I.E.L.D agents. After being injured in her work she received a commendation by then S.H.I.E.L.D. Director Nick Fury, who used her information to expose dozens of subversives within S.H.I.E.L.D. Resigning from S.H.I.E.L.D., Mockingbird was hired to investigate Cross Technological Enterprises (CTE), where she clashed with security director Hawkeye. The two soon discovered that CTE was working for the criminal Crossfire helping to implement his plans to brainwash super heroes into killing each other off. The two joined forces against Crossfire and his underlings, becoming attracted to each other in the process. At the case’s successful conclusion, Mockingbird proposed to Hawkeye and the two married. When Hawkeye was appointed head of the West Coast branch of the Avengers, Mockingbird became the team's first new recruit and was instrumental in helping Hawkeye form the new team.
Months later, during a time traveling adventure in 1876, Mockingbird was abducted, drugged and abused by the crazed vigilante called the Phantom Rider (Lincoln Slade), who attempted to force her to become his bride. Regaining her senses, Mockingbird fought the Rider to a cliff’s edge and allowed him to fall to his death. After the West Coast Avengers returned to their home era, Mockingbird kept the nature of the Phantom Rider’s death a secret. However, the Rider’s ghost soon appeared and told the Avengers that she had been instrumental in his death, and had essentially murdered him. Distraught that an Avenger (especially his wife) had allowed a man to die, Hawkeye became estranged from his wife, and Mockingbird re-entered into government service. She participated in Operation: Vigilance, a program to provide protection from any potential threat from the Vision, only to rebel once she discovered the program's full agenda. Helping the Avengers to rescue the Vision, she was gradually reconciled with Hawkeye, though their relationship never fully recovered. Together they helped train the Great Lakes Avengers and Mockingbird became good friends with Ashley Crawford.
Mockingbird was abducted by the Skrull shortly after returning to the West Coast Avengers, as she was attempting to discuss divorce with Hawkeye. Replaced by a Skrull duplicate, her absence was not discovered before the doppleganger’s death at the hands of the demonic Mephisto. On the Skrull homeworld, Mockingbird was confronted by a duplicate Hawkeye who became obsessed with her and stalked her as she gathered information on the Skrull’s secret invasion plan. After three years at the hands of the Skrulls, she was reunited with Clint Barton (then in the guise of Ronin), founded the World Counter-terrorism Agency with the S.H.I.E.L.D. agents that defected at the start of Norman Osborn’s Dark Reign, and joined the Avengers alongside her ex-husband.